1. Field of Invention
This invention relates to methods and apparatus for wavelength reuse.
2. Description of Related Art
Data transmissions often require that multiple transmissions of a same wavelength along a same medium be avoided. When multiple transmissions for a single wavelength propagate along a same medium (optical fiber, coax, twisted pair, etc.), the multiple transmissions may collide, interact or conflict with each other causing reduction in signal quality such as lower signal to noise ratio or increased cross talk, for example. Thus, new technology is needed to avoid transmission conflicts.
This invention provides methods for assigning wavelengths and apparatus for using the assigned wavelengths. Nodes of a network are interconnected to adjacent nodes via either a unidirectional or bidirectional connection. Wavelengths are assigned to destination nodes so that transmissions from any node within the network traverses connections and nodes until the transmission is received by a destination node. The destination node receives transmissions of assigned wavelengths and prevents the transmissions from being further transmitted so that a transmission propagates within the network until received by the destination node.
The invention assigns wavelengths to nodes in such a way that wavelengths may be reused, thus achieving a minimum number of wavelengths for any network. First, a starting node and a direction is selected within the network. Nxe2x88x921 wavelengths are assigned to the starting node where N is a number of nodes in the network. A second node adjacent to the starting node is selected and Nxe2x88x921 wavelengths already assigned to the starting node are tentatively assigned to the second node while avoiding conflicts where possible. A conflict occurs when a transmission by the second node to a destination node may traverse a connection that may already be traversed by a transmission of the same wavelength by the starting node. New wavelengths are assigned to the second node for destination nodes of which no prior assigned wavelengths may be used due to conflicts. Then, a third node is selected and wavelengths are assigned as for the second node except all prior assigned wavelengths are tested for conflicts first before assigning new wavelengths. The process continues until all the nodes are selected and wavelengths assigned. The above assignment may be applied for unidirectional or bidirectional connections. For bidirectional connections, the same wavelength may be used for transmission in both directions without a conflict.